1 // SPDX-License-Identifier: GPL-2.0 2 /* Copyright (c) 2024 ByteDance */ 3 #include <linux/bpf.h> 4 #include <bpf/bpf_helpers.h> 5 6 struct { 7 __uint(type, BPF_MAP_TYPE_SOCKMAP); 8 __uint(max_entries, 1); 9 __type(key, int); 10 __type(value, int); 11 } sock_map_rx SEC(".maps"); 12 13 long change_tail_ret = 1; 14 15 SEC("sk_skb") 16 int prog_skb_verdict(struct __sk_buff *skb) 17 { 18 char *data, *data_end; 19 20 bpf_skb_pull_data(skb, 1); 21 data = (char *)(unsigned long)skb->data; 22 data_end = (char *)(unsigned long)skb->data_end; 23 24 if (data + 1 > data_end) 25 return SK_PASS; 26 27 if (data[0] == 'T') { /* Trim the packet */ 28 change_tail_ret = bpf_skb_change_tail(skb, skb->len - 1, 0); 29 return SK_PASS; 30 } else if (data[0] == 'G') { /* Grow the packet */ 31 change_tail_ret = bpf_skb_change_tail(skb, skb->len + 1, 0); 32 return SK_PASS; 33 } else if (data[0] == 'E') { /* Error */ 34 change_tail_ret = bpf_skb_change_tail(skb, 65535, 0); 35 return SK_PASS; 36 } 37 return SK_PASS; 38 } 39 40 char _license[] SEC("license") = "GPL"; 41